In this lecture, we will consider how to transfer from one orbit, or trajectory, to another. One of the assumptions that we shall make is that the velocity changes of the spacecraft, due to the propulsive effects, occur instantaneously. Although it obviously takes some time for the spacecraft to accelerate to the velocity of the new orbit, this assumption is reasonable when the burn time of the rocket is much smaller than the period of the orbit. In such cases, the Av required to do the maneuver is simply the difference between the

When the only force acting on a particle is always directed to- wards a fixed point, the motion is called central force motion. This type of motion is particularly relevant when studying the orbital movement of planets and satellites. The laws which gov- ern this motion were first postulated by Kepler and deduced from observation. In this lecture, we will see that these laws are a con- sequence of Newton's second law. An understanding of central

Solution General solution x(t)= A cos wnt +B sin wnt or, x(t)=Csin(wnt+φ) Initial conditions

Lecture D32: Damped Free Vibration Spring-Dashpot-Mass System k Spring Force Fs =-kx, k>0 Dashpot Fd =-cx, c>0 Newton's Second Law (mx =EF) mx +cx+kx (Define)Natural Frequency wn=k/m,and

一、名词解释 复出口:外国商品进口以后未经加工制造又出口 (reexport). 复进口:本国商品运往国外未经加工后又输入国内 (reimport)

第一节国际无形贸易概述 第二节与国际服务贸易有关的一些行业

商品的品质:商品的外观形态和内在质量的综合, 是商品满足用户需要、适合一定用途的各种特 征。 在书面合同中,商品品质条件列在“货号、品 名和规格”栏目内,是国际贸易合同中主要的 交易条件之一

商品检验(Commodity Inspection) 国家设置的检验管理机构或政府认可的民间公 证鉴定机关对国际贸易中的商品进行品质、数 量、包装、卫生、安全及残损、短缺的检验和 鉴定,根据检验结果出具商检证书。 国际贸易合同中的商检条款内容 通常包括对商检时间、地点、检验机关、检验 证书等内容的规定

一、绝对成本理论(Absolute Cost Theory) 绝对成本理论的基本结论: 在商品生产中,每一个国家都有自己拥有生产优 势的产品。各国应该生产具有绝对优势的产品去 交换本国必需的但自己生产又处于绝对不利地位 的产品,从而使本国的土地、劳动和资本得到最 有效的利用,提高劳动生产率,增加社会财富

经济一体化(Economic Integration) 两个或两个以上国家(地区)为维护共同的经济和 政治利益,通过协调、缔结条约或协定,实施共同 政策与措施,结成单一的、排他性的经济实体甚 至政治联盟。 经济一体化是当前世界经济发展的总趋势,具体 表现为: